Consumer electronic products, for example, portable devices such as smart phones, pads, tablets, laptops and digital cameras, have been rapidly developed and commercialized. To function as a digital camera, these smart phones, pads, tablets and laptops are typically equipped with one or more camera modules to capture images or videos. Digital cameras and camera modules can sense light using a semiconductor sensor, a common example of which is Complementary Metal-Oxide Semiconductor (CMOS) image sensor.
A CMOS image sensor includes a 2D (two dimension) array of pixels arranged in rows and columns, and a row decoder to control operation of the pixels. The row decoder includes a plurality of row-level decoders, the number of which corresponds to the number of the pixel rows, and each row-level decoder may drive a respective row of pixels. The row-level driver often requires a plurality of high and low voltages for its operation. However, logic control signals are usually in a low voltage domain, which cannot serve directly as the required high and low voltages. To solve this problem, voltage level shifters are needed in each row-level decoder to drive the high and low voltages.
As the resolution of the CMOS in sensor is continuously improved, the number of the pixel rows included in the CMOS image sensor increases accordingly. As a result, more and more row-level decoders are deployed in the CMOS image sensor to drive the pixel rows. These tow-level decoders consume a significant portion of the layout area and increase the overall cost of the image sensor.
Therefore, there exists a need for a compact row decoder that is capable of providing multiple voltage support. Advantageously, the present invention provides a solution that can meet such a need. The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.